Method of making hollow propellers



Dec. 11, 1945. o. s. HASKELL 2,390,789

METHOD OF MAKING HOLLOW PROPELLERS Filed Aug; 17, 1942 Ihvntor Orin S.HasKell Patented Dec. 11, 1945 METHOD OF MAKING HOLLOW PROPELLERS OrinS. Haskell, Schenectady, N. Y., assignor to General Electric Company, acorporation of New York Application August 17, 1942, Serial No. 455,027

1 Claim.

The present invention relates to hollow propellers as are used forpropelling aircraft. More particularly, the invention relates to thekind of propellers made from steel tubing by a forming process. Suchpropellers hav blades airfoil-shaped in section with a pitch varyingfrom the root to the tip. The edge portions of the blades are subject toconsiderable forces during operation and therefore reinforcing meansnear the edges inside the hollow blades must be provided to precludefailure due to excessive stresses along the edge portions. At present itis the practice to produce such reinforcing means in the form of filletsfrom copper cast into the edge portions of the blade. The process ofcasting the reinforcing fillets or strips is ordinarily carried out in anumber of successive steps during each of which an amount of copper iscast into a portion only of the hollow edge. This succession of stepsheretofore has been found necessary properly to distribute the meltedreinforcing material over the entire length of the edge. The presentmethod is especially cumbersome in regard to modern propeller bladeswith considerable variation of the pitch from the root to th tip.

Th object of my invention is to provide an improved method ofmanufacturing impellers, more particularly of producing the reinforcingmeans near the hollow edge portions thereof whereby the aforementioneddifliculties are substantially eliminated.

Another object of my invention is to provide a method f making animproved propeller blade structure in which the weight of the reinforcededge portions is kept at a minmum. This is accom lished in accordancewith my invention by the provision of a reinforcing stripmade fromresilient flexible steel united with the hollow edge portions by ablazing process.

During the method of manufacture a strip in the form of around orotherwise suitably shaped wire is inserted into the hollow bladetogether with another strip of copper, and the blade with the copper andsteel strips inserted in the edge portions is placed into a blazingfurnace to effect brazing of the steel strips to opposite sides of thehollow edge portion.

For a better understanding of what I believe to be novel and myinvention, attention is directed to the following description and theclaim appended thereto in connection with the accompanying drawing.

In the drawing Fig. 1 illustrates a propeller according to my invention;Fig. 2 shows a propeller. blade during the process of manufactureaccorda forming process.

ing to my invention; Fig. 3 is an enlarged section along lin 3-3 of Fig.2; Fig. 4 is an enlarged edge portion of the blade shown in Figs.- 2 and3 upon completion of the process according to my invention; and Figs. 5and 6 illustrate sectional Views of modifications of my invention.

The propeller in Fig. 1 has three blades ill with inner end portions orroots secured to a support or hub I I. The blades are of conventionalshape, the root portion is essentially cylindrical, and the blade tapersgradually outward up to a certain point from which it gradually tapersinward to assume a leaf shape, as indicated in Fig. 2. In cross sectionthe blade is air-foil-shaped, as shown in Fig. 3. The pitch, that is,the angle between the horizontal center-line of the section in Fig. 3and the plane of rotation, varies gradually from the root towards thetip. This complicated shape is attained by subjecting a hollow tube toThe opposite walls of the tip portion upon completion of the formingprocess are united by a fusion process, such as stitchwelding.

During operation, different parts of the propeller are subject todifferent stresses. These stresses are especially great with regard toportions slightly spaced from the inner edge and considerably spacedfrom the center of the blade when viewed in Fig. 3. In order to carrythe load acting on these portions a propeller blade according to myinvention is reinforced by a strip l2 (Fig. 4) of steel rigidly securedto opposite walls of the propeller blade near its edge by a brazingprocess.

During the process of forming the reinforcing strip 12 a steel wire I3is inserted into the hollow blade body in the form of a loop (Fig. 2).The resilency of the wire material forces the wire into the hollow edgeportion. Together with the wire suitable brazing material is insertedinto the body. This material is preferably in the form of a copper wire14 (Fig. 2) of a cross section smaller than that of the steel wire [3and placed into the edge of the blade body. The blade body with thesteel and copper wires is then placed into a brazing furnace and subjectto high temperature at which the copper is melted to effect a strongbond between the blade and the inserted steel wire, as shown in Fig. 4.In certain instances it may be desirable to use a plurality of thinsteel wires I5 together with a single strip or wire of copper l6 (Fig.5) in place of the single wires [3, I 4 respectively in Figs. 2 and 3.In other instances (Fig. 6) a steel wire I! to be inserted into thehollow edge portion of a blade may be shaped so that its opposite sidesconform to the shape of the inner surfaces of the bladebody. The crosssectional area of the wires I! may vary along the edge of the blade(Fig. 6) so as to provide for difierent reinforcement as may be requiredfor difierent edge portion of a blade. The copper Wire [8 used in Fig. 6is likewise shaped to conform to the edge-of the blade and in certaininstances it may bedesirable to secure the copper wire [8 to the steelwire I! prior to their insertion into the blade.

Thus, with my invention I have provided an improved propeller bladestructure and method of making the same. The fillet or reinforcing stripis united to the edge portions of a propeller blade by a brazing processin' a single step.

Having described the method according to my invention, together with theapparatus for carry.. ing out the method, I wish to have it understoodthat changes may be made in both the apparatus of the steel stripforcing opposite portions of the loop into the hollow edge portions ofthe blade, and subjecting the body with the two strips therein to abrazing operation integrally to unite in a single step'the steel stripand the walls of the body near the inner edge thereof.

ORIN S. HASKELL.

